Advances in conventional therapies are increasingly successful in imaging and sterilizing a brain tumor mass. New approaches are needed to attack the disseminated or infiltrating tumor that remains. This has led to renewed interest in immunotherapy as an adjunctive mode of treatment. Hypothesis: 1. In the tumor-bearing brain, intracerebral injection of IFN-g can activate antigen-presenting cells and recruit primed helper T cells. 2. If the T cells have been primed to tumor antigen, the resulting immune cascade can lead to the destruction of disseminated brain tumor cells. Specific aims to test the hypothesis: I. When rats have been immunized to neural or tumor antigen, will intracerebral injection of IFN-g cause helper T cells to migrate through the brain? II. Can IFN-g treatment and immunization act synergistically to control the spread of tumor cells within the brain? A. Does IFN-g treatment alone reduce tumor spread? B. Do [IFN-g treatment + immunization] work synergistically to reduce tumor spread? C. Can [IFN-g treatment + immunization] cure residual disease remaining after surgery or radiation therapy? Methods: These studies will be performed in a rat model, in vivo. Stereotactic surgery, histochemistry and immunohistochemistry will be used.